Medically intractable temporal lobe epilepsy (TLE) is often treated by surgical removal of the anterior tip of the temporal lobe and the entire hippocampus. This tissue affords an unique opportunity for examining the characteristics of a human epileptogenic focus. Such information could also proove useful to the surgeon for development new strategies for in activating a seizure focus. This proposal aims at examining human epileptogenic tissue and testing the hypothesis that its increased excitability could be found in the reorganization of its neurotransmitter systems and/or the processes that mediate neurotransmitter action. To this and the distribution of nertotransmitter receptor systems for glutamate (GLU), GABA, somatostatin (SOM), neuropeptide Y (NPY) and dynorphin (DYN) will be studied with autoradiographic methods. The 2nd messenger adenylate cyclase and phosphoinositide systems will be localized with (3H)PDBu to label protein kinase C, (3H)IP3 to tag the IP3 receptor, and (3H)-forskolin to label the Gs adenylate cyclase complex. In order to assess the biosynthesis of the peptides SOM, NPY and DYN, in situ hybridization experiments will be done. Further, the distribution of the protooncogene protein c-fos will be examined immunocytochemically to determine if it is involved in human seizures as in animals. Giant 2D gel electrophoresis of epileptogenic tissue will attempt to identify any proteins unit to the seizure focus. Rats with heat induced seizures will be evaluated is a model for human TLE of non-tumor origin, and for the study of febrile seizures and the developmental outcome of such seizures. 2-deoxyglucose mapping of metabolic activity and for expression will be used to determine the origin and spread of seizures in these rats. Neuronal counts; light and electron microscopic immunocytochemical localization of neuroactive substances (GABA, Glutamate, SOM, NPY, DYN); autoradiographic mapping of the receptors for these substances; and second messenger systems; along with in situ hybridization experiments for peptide biosynthesis will determine the similarity of the changes induced by seizures in the rat to those of the human. The consequences of seizures induced in neonatel rats on their adult hippocampal organization will be evaluated to determine if there are sensitive periods during which febrile seizures lead to adult onset seizures.